1. Field of the Invention
The present invention relates in general to a hand tremor compensating apparatus for a video camera using magnets, and more particularly to a hand tremor compensating apparatus for a video camera, wherein a mirror section of the hand tremor compensating apparatus is secured by a magnetic force, so that the mirror section is restrained from rotating in the circumferential direction thereof when a bobbin is driven, thereby effectively compensating the hand tremor phenomenon.
2. Description of the Related Art
A video camera shoots, records and reproduces a picture. The video camera is manufactured in a small size to permit the user to easily carry the video camera.
Since the user manually takes a picture, a hand tremor phenomenon occurs that causes reproduced images to be dispersed. The hand tremor phenomenon can be reduced by various camera techniques. However, the phenomenon still scatters the focus of the reproduced images. In particular, when the reproduced image is magnified and projected onto a large screen, a distinct picture cannot be obtained due to the hand tremor phenomenon.
In order to solve the above problem, a hand tremor compensating apparatus as shown in FIGS. 1 and 2 has been suggested. Conventional video cameras, therefore, comprise a camera section and a hand tremor compensating apparatus.
The camera section includes a case 2 having a window 1 at a front end thereof, a lens holder 3 installed in the case 2, a barrel master 4 coupled to a rear portion of the lens holder 3, and a solid-state image pickup device fixedly coupled to a rear wall of the barrel master 4 for recording image information based on an incident beam from an object.
A lens group including a focus lens 7 for focusing the incident beam and a zoom lens 6 for enlarging or reducing the magnification of the incident beam is mounted in the lens holder 3 and the barrel master 4. Coupled between the lens holder 3 and the barrel master 4 is an iris for adjusting an amount of the incident beam.
A charge coupled device (hereinafter referred to as a CCD) 5 transforms the incident beam into electric information, thereby generating image information.
As shown in FIG. 2, the hand tremor compensating apparatus includes a mirror section 8 disposed between the object and the lens group, a bobbin 9 having a hemisphere-shaped contact portion 9a for protecting and supporting the mirror section 8, a barrel 10 disposed about an outside of the bobbin 9, and a hand tremor compensating member.
The contact portion 9a protrudes from the center of an underside of the bobbin 9, and is provided at its outer circumference with a spring rack 9b.
A boss 11 extends along a center of the barrel 10. The boss 11 has a hollow portion 11a into which a post 12 is screw-coupled. One end of a spring 13 is connected to the post 12, and the other end of the spring 13 is connected to the spring rack 9b. Accordingly, the spring 13 influences the center point of the bobbin 9 to align with the boss 11 when the bobbin 9 is moved in the rolling and pitch directions. The tension of the spring 13 is adjustable by adjusting the insertion position of the post 12 within the hollow portion 11a of the boss 11.
A light emitting diode 14 is fixed to one side of the bobbin 9. A light receiving diode 15 is fixed to an upper side of the barrel 10 in line with the light emitting diode 14. The light emitting diode 14 and light receiving diode 15 recognize a number of rotation times and an angle of the mirror section 8 when compensating for the hand tremor.
The hand tremor compensating member includes a rolling actuator and a pitch actuator 16 which provide a driving force for driving the bobbin 9 in the rolling and pitch directions. The pitch actuator 16 has the same construction as the rolling actuator and is disposed perpendicular to the rolling actuator. Only the pitch actuator 16 is shown in the figures.
The pitch actuator 16 includes a support 17 fixed to a lower portion of the bobbin 9, a coil 18 wound around one end of the support 17, a magnet 19 which interacts with a magnetic field generated by the coil 18, and a voice coil motor having a U-shaped yoke 20. Magnet 19 is attached to an inner side wall of the U-shaped yoke 20.
In the structure mentioned above, the incident beam from the object passes through the window 1 and is reflected by the mirror section 8. The incident beam, reflected at a right angle, is introduced into the CCD 5 through the lens group such as a zoom lens 6 and a focus lens 7.
At this time, an angular velocity sensor detects the hand tremor, if any occurs, and sends a signal to the rolling and pitch actuators 16.
The rolling and pitch actuators 16 operate upon receiving the signals from the sensor. That is, when an electric current is applied to the coil 18, the support 17 moves up and down as a result of the magnetic interaction between the coil 18 and the magnet 19.
Accordingly, the bobbin 9 including the mirror section 8 is finely driven in the rolling and pitch directions due to the up and down movement of support 17.
At this time, light emitting diode 14 and light receiving diode 15 recognize a number of rotation times and an angle of the mirror section 8 and control the mirror section 8 in the rolling and pitch directions, thereby compensating for the hand tremor.
In addition, when the bobbin 9 is driven, the influence of the spring 13 prevents the bobbin 9 from moving away from the boss 11, such that the contact between the contact portion 9a and the upper surface of the boss 11 is maintained. Accordingly, the gap between the bobbin 9 and the boss 11 is fixed. Further, the spring 13 prevents the bobbin 9 from rotating in the circumferential direction.
Since the gap and the center point of the bobbin with respect to the boss are constantly maintained by the spring 13, it is difficult to precisely adjust the insertion position of the post 12 for adjusting the tension and the length of the spring 13. In addition, assembling the spring into the hand tremor apparatus is difficult.
Further, if the elasticity of the spring 13 changes, the gap between the bobbin 13 and the boss 11 cannot be constantly maintained. For this reason, the alignment of the center point of the bobbin 9 with respect to the boss cannot be maintained.
In addition, since a tremor occurs in the spring when compensating for the hand tremor by driving the rolling and pitch actuators, the hand tremor compensating is not sufficiently carried out.